2o6 VOL UT1ON AND DISEASE. 



mammal. The centre of every growing tooth is occupied 

 by a cavity known as the pulp chamber, which in the 

 living tooth is filled with connective tissue, blood-vessels, 

 nerves, and cells known as odontoblasts. The tissues 

 constituting the pulp are actively engaged in forming 

 dentine ; in teeth and tusks with persistent pulps this 

 pulp chamber is always relatively large, and as the tooth 

 is worn at the apex the pulp adds new material at the 

 base. In teeth with non-persistent pulps, like those of 

 primates, carnivora, and the like, the pulp chamber 

 diminishes with age, and in some the pulp becomes 

 converted into bony substance known as osteo dentine. 

 When teeth become inflamed or carious the pulp often 

 calcifies, and it is no unusual event to find in a carious 

 tooth extensive ossification of the pulp in the neighbour- 

 hood of the carious cavity : this is salutary, for by this 

 means suppuration of the pulp is prevented and often 

 a tooth remains serviceable much longer than would 

 otherwise be the case. 



Ivory-turners have often found in the tusks of ele- 

 phants such things as bullets, iron slugs, and spear-heads, 

 yet on an attentive examination no trace of injury 

 could be detected on the exterior of the tusk. These 

 specimens attracted the attention of investigators such 

 as Blumenbach, Haller, Cuvier, Goodsir, and Owen. The 

 solution of the mystery was indicated by a study of the 

 material surrounding the foreign body. Cuvier detected 

 the irregularity of the dentine immediately surrounding 

 the bullet, and Goodsir made an elaborate study of the 

 whole question, and it became clear from the researches 

 of Goodsir, Nasymth, and Owen, that this irregular 



